1. Field of the Invention
This invention relates to a motor constructed super-compactly.
2. Related Background Art
Heretofore, as a motor formed as a compact motor, there is, for example, a compact cylindrically shaped step motor as shown in FIG. 24 of the accompanying drawings.
In FIG. 24, this motor is provided with two stators 102 arranged axially of the motor, and each of the stators 102 has two stator yokes 106 disposed so as to be axially opposed to each other. In each stator 102, a stator coil 105 is concentrically wound on a bobbin 101 held by the two stator yokes 106. Each bobbin 101 having the stator coil 105 wound thereon is axially sandwiched and fixed by and between the two stator yokes 106. Each of the stator yokes 106, 106 is formed with stator teeth 106a and 106b alternately disposed circumferentially of the inner diametral surface of the bobbin 101. On the other hand, the pair of stator yokes 106 and 106 having the stator teeth 106a and 106b are fixed to the case 103 of each stator 102. Thus, the stators 102 are constructed.
A flange 115 and a bearing 108 are fixed to one (the left one as viewed in FIG. 24) of the two sets of case 103, and a bearing 108 on the opposite side is fixed to the other (the right one as viewed in FIG. 24) case 103. A rotor 109 is of such a structure that a rotor magnet 111 is fixed to a rotor shaft 110. An air gap is formed between the outer peripheral surface of the rotor magnet 111 and the inner diametral surface of the stator yoke 106 of the stator 102. The rotor shaft 110 is rotatably supported by the two bearings 108 fixed to each case 103.
FIG. 26 of the accompanying drawings is a plan view exemplifying a step motor driven by a coil which is used in a timepiece or the like. In FIG. 26, reference numeral 201 designates a rotor comprising a permanent magnet, reference numerals 202 and 203 denote stators, and reference numeral 204 designates a coil.
However, in the prior art compact step motor shown in FIG. 24, the case 103, the bobbin 101, the stator coil 105 and the stator yoke 106 are concentrically disposed around the rotor, and this leads to the inconvenience that the outside dimension of the motor becomes large. Also, a magnetic flux created by the electrical energization of the stator coils 105 passes chiefly through the end surface 106a1 of the stator tooth 106a and the end surface 106b1 of the stator tooth 106b, as shown in FIG. 25 of the accompanying drawings and therefore does not effectively act on the rotor magnet 111, and there is the problem left to be solved that the output of the motor does not become high. Also, in the motor shown in FIG. 26, there is the problem left to be solved that a magnetic flux created by the electrical energization of the coil 204 concentrates in the portion of a small gap between the rotor 201 and the stator 202 and does not effectively act on the magnet 201.
The applicant of the basic application in Japan has proposed as U.S. Pat. No. 5,831,356 a motor which has solved such problems.
This proposed motor is designed such that a rotor comprising a permanent magnet circumferentially equidistantly divided and alternately magnetized to different poles is formed into a cylindrical shape, a first coil, the rotor and a second coil are disposed axially of the rotor in the named order, a first outer magnetic pole and a first inner magnetic pole excited by the first coil are opposed to the outer peripheral surface and inner peripheral surface, respectively, of the rotor, and a second outer magnetic pole and a second inner magnetic pole excited by the second coil are opposed to the outer peripheral surface and inner peripheral surface, respectively, of the rotor, and a rotary shaft, which is a rotor shaft, is taken out of the cylindrically shaped permanent magnet.
The motor of such a construction is high in output and can have its outside dimension made small, but the working of its magnetic pole teeth is difficult because the diametral dimension of its inner magnetic poles is small, and it has been desired that a stable output free of fluctuation be obtained from a motor of a small diametral dimension.
Therefore, the applicant of the basic application filed in Japan has recently proposed a motor in which the shape of inner magnetic poles is made readily workable as U.S. patent application Ser. No. 08/994,994, and a rotor, in which output transmitting means, such as gears and pulleys, are easily mounted on a rotary shaft of small diametral dimension to thereby obtain a stable output free of fluctuation, has been proposed as U.S. patent application Ser. No. 09/022,474.
Recently, it has been desired that a motor having a high output and which can be constructed super-compactly be obtained.
The present invention has been made in view of the above-noted circumstances and an object thereof is to provide a motor which is high in output and is constructed more super-compactly.
Another object of the present invention is to stabilize the positioning of a rotor when a motor is made into a one-phase motor.
Further objects of the present invention will become apparent from the following description of some specific embodiments of the invention.